The present invention relates to a side air bag which expands near a window of a vehicle at a collision of the vehicle, and particularly relates to a side air bag formed by a woven fabric such as a hollow weave.
An air bag apparatus for a vehicle is an apparatus for constraining a vehicle occupant, i.e. passengers and a driver, by inflating and expanding an air bag at a time of collision of the vehicle, and generally comprises an inflator (a gas generating device) for inflating the air bag in response to a signal from a sensor for detecting a  predetermined collision characteristics of the vehicle. The air bag is inflated by gas from the inflator. The air bag is formed in a bag shape by a woven fabric.
A so-called hollow weave, in which two fabrics are interwoven as a  one woven fabric and  by a yarn, partly constituting each of the two fabrics, partly to form a common textile structure so as to combine  of the interwoven two fabrics, is generally known in weaving for producing industrial materials and the like. There are some examples in which the woven fabric of the hollow weave is used for ane  an air bag, for example, JP-A-02158442 (Japanese Patent Unexamined Publication No. 2-158442) describes a bag formed by the hollow weave. JP-A-03128743 describes that  connection of the  woven fabric  fabrics in the  a peripheral portion is performed  by a single-layer joint textile structure for connection , and similar matter is described in PCT  WO90/09295 (PCT/GB90/00215, Japanese Patent National Publication of translated version 4-504988) .
However, the air bags of these references are basically uncoated bags which are woven by hollow weave. The references disclose that air bags can be partly coated or coated, but have no intention for reducing an air-permeability of a fabric by coating.
On the other hand, while  While the conventional air bag apparatus includes both an air bag for a driver's seat,  and an air bag for a front-passenger seat and the like, a common point thereof is to constrain an occupant from the front within a short time such as some milliseconds to some ten  tens of milliseconds.
Recently, as an air bag apparatus, in  In addition to the above air bag apparatus which constrains the occupant from the front, a side air bag apparatus for constraining the occupant from a left-hand side or a right-hand side is developed  known.
The side air bag is structured such as to be housed in a side structure of the vehicle such as a front pillar, a roof side rail portion, a center pillar, a quarter pillar and the like, and as to receive  receives a gas supplied from an inflator fixed to a bottom part of the front pillar or a neighboring side panel and the like at a time when the vehicle receives a predetermined impact from the side surface thereof so that the air bag inflates and expands near the window along a side surface of a cabin, thereby restraining the occupant from moving in a lateral direction of the vehicle.
A point in which the  The side air bag is greatly  different from the above typical-type conventional  described air bag is  in that a long expanding time, such as some seconds, is required to be continued for constraining the occupant at a time of overturning of the vehicle.
Accordingly, the typical-type conventional  above described air bag has a function of inflating and expanding for a short time, such as some milliseconds, to some ten  tens of milliseconds and of discharging the gas while constraining the occupant. In contrast to this, in the newly suggested  side air bag, to meet a constraint requirement of the occupant at a time of overturning of the vehicle, it is required to set  have an expansion holding time to  for a relatively long time such as some seconds.
Further, the typical-type conventional  air bag mentioned above for front collision operation is housed in a relatively large size trim part of the vehicle, such as a horn pad, an instrumental panel, a seat or the like, and a cross sectional area of the air bag in a direction of folded and piled fabrics is about 20 to 150 cm2. However, in the side air bag, since it is housed in a column shaped pillar, a roof side rail portion or the like, there is a problem that the side air bag has to be folded in a relatively small cross sectional area such as 4 cm2 so as to be housed .